Pneumatic tool



May 18, 1965 H. A. DEFOE, JR 3,183,786

PNEUMATIC TOOL Filed Aug.' 28, 1965 BY Z6 M Arrow/l United States Patent G 3,183,786 PNEUMATIC TOOL Howard A. Defoe, Jr., 11 Rambo Drive, Rambleton Acres, New Castle, Del. Filed Aug. 28, 1963, Ser. No. 305,155 4 Claims. (Cl. 91-232) This invention relates to pneumatic tools and more particularly to small pneumatic tools which use a reciprocating motion for tiling, abrading, polishing or similar operations.

Existing pnuematic tools employ a valving piston or other complicated valving mechanisms with an operating piston to reciprocatingly drive a tool bit. Such devices are not only costly to make but are costly to maintain since the many parts frequently require replacement or repair. Additionally, such tools are bulky and therefore cumbersome to use. Moreover, the effective life of many pneumatic tools is greatly reduced by the frequent impacts of the piston against the ends of the housing and by the use of the piston interior for fluid passages since the piston is thereby weakened.

Accordingly, an object of this invention is to provide a pneumatic tool which is simple in construction and in operation without sacrifice to its eifectiveness or durability.

In accordance with this invention, the operating piston also acts as a valving piston. This is accomplished by providing channels in the piston and in the housing for alternately directing fluid to chambers in each end of the housing. Since the piston is of relatively small mass and has small inertia, it changes its direction quickly enough to valve the ow of fluid as well as to drive the tool bit.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIG. l is a perspective view of an embodiment of this invention;

FIG. 2 is a longitudinal cross-sectional view taken through the center of the tool shown in FIG. 1 with the piston in its rearmost position;

FIG. 3 is a longitudinal cross-sectional view taken through the center of the tool shown in FIGS. 1-2 with the piston in its foremost position;

FIG. 4 is a longitudinal cross-sectional view taken through the center of an outer shell member of the embodiment of the invention shown in FIGS. 1-3;

FIG. 5 is an end elevation view of the shell member shown in FIG. 4;

FIG. 6 is a longitudinal cross-sectional view taken through the center of an inner shell member of the embodiment of the invention shown in FIGS. 1-3;

FIG. 7 is an end elevation of the shell member shown in FIG. 6;

FIG. S is a cross-sectional view in elevation taken through FIG. Z along the line 8 8;

FIG. 9 is a cr0ss-sectional view in elevation taken through FIG. 2 along the line 9 9;

FIG. 10 is a cross-sectional view in elevation taken through FIG. 2 along the line 1li-1G; and

FIG. ll is an end view of the embodiment of the invention shown in FIGS. 1 3 showing the fluid connection means.

As shown in FIGS. 1-3, pneumatic tool 10 comprises a housing 12 of a size to be held comfortably in one hand 14. Housing 12 includes an outer shell 16 and an inner shell 18 while an extension section 20 is attached to housing 12 by means of pins 22. Secured to the rear portion of housing 12 is a cover member which substan- 3,183,786 Patented May 18, 1965 tially seals the rear portion of the housing against escape of lfluid and which has a fluid inlet 26 including a valve 28 such as a needle valve. Hose 27 is attached to fluid inlet 26 and leads to a source of uid under pressure. Operating piston 30 intimately reciprocates in housing 12. Integral with piston 30 is a tool bit holder 34 which telescopes through housing 12 and reciprocatingly slides in guide bearing 36 at the foremost end of housing extension 2i?. Guide bearing 36 also effectively seals the front portion of housing 12 against escape of uid. Pin 3S secured to shaft 34 through a slot in housing extension 20 and in guide bearing 36 prevents shaft 34 from rotating. Chuck means such as lock screw 40 secures tool bit 42 to holder 34. Tool bit 42 is shown to be a file in FIG. 1, but it may be any type of tool bit which operates by reciprocating motion such as a saw, polisher or a sander.

Tool bit 42 is driven by the pressure of fluid which ows through a series of channels or passages and finally strikes operating piston 30. Operating piston 30 also acts as a valving piston. This is possible because piston 39 is of relatively small mass and small inertia and thus can change its direction quickly enough to valve the flow of fluid. As later described, piston 30 is provided with grooves or channels which open and close the flow of fluid through the Various passages so that the fluid is alternately supplied to rear chamber 43 and front chamber 45 of housing 12. The channels or passages in housing 12 are formed by providing channels in inner shell 18 and covering inner shell 18 with an imperforate outer shell 16. Fluid entering inlet 26 goes through drive passage 44. As shown in FIG. 2, when piston 30 is in its rearmost position, branch 45 of drive passage 44 communicates with forward stroke passage 4S through groove 50 in piston 30. Fluid then enters rear chamber 43 of housing 12 through forward stroke passage 48. When piston 30 is in the position shown in FIG. 2, exhaust port 52 is closed and pressure builds in the back of piston 30 to drive the piston in its forward stroke.

Exhaust ports 52 and 54 are provided in each end of honing 12 to permit the escape of fluid from the housing. The distance between exhaust ports S2 and 54 is slightly larger than the length of piston 30 so that both ports can never be completely open or completely closed at the same time, as shown in FIGS. 2 and 3. Further, the distance between branches 46 and 60 of drive passage 44 is substantially equal to the distance between forward stroke passage outlet 47 and return stroke passage outlet 55 and is also substantially equal to the distance between piston grooves 50 and 58 plus the width of one of the grooves so that return stroke passage 56 begins to open when forward stroke passage 48 begins to close and forward stroke passage 4S begins to open when return stroke passage 56 begins to close. Additionally, the distance between exhaust port 52 and forward stroke passage outlet 47 is substantially equal to the distance between ex haust port 54 and return stroke passage outlet 55 so that exhaust port 52 begins to open when forward stroke passage 48 begins to close and exhaust port 54 begins to open when return stroke passage 56 begins to close. Forward stroke passage 48 is longer than return stroke passage 56 and thus holds more uid so that more pressure builds up in rear chamber 43 of housing 12. As a result, the forward stroke is stronger than the return stroke.

When piston 30 is in its forward stroke, return stroke passage 55 begins to open as piston groove 58 moves into communication with drive passage branch 60 and return stroke passage outlet 55. Pressure then begins to build in front chamber 45 of housing 12. The pressure in rear chamber 43, however, is greater than the pressure in the front chamber so that piston 30 continues to move in its forward stroke until the piston is in its foremost position, as shown in FIG. 3. Resilient means 62 prevents piston 30 from striking housing 12.

After piston 30 is in the position shown in FIG. 3, the reverse procedure takes place and piston S0 is moved in its return stroke while resilient means 64 prevents the piston from striking housing 12.

Using the aforementioned tool, the operator conveniently holds the tool in one hand, as shown in FIG. 1, similar to the way a pencil is held, and then simply guides the tool. The simplicity in the operation of tool l() permits the operator to achieve a high degree of accuracy in his work without sacrifice to ease and convenience.

What is claimed is:

l. A pneumatic to'ol comprising a slender elongated housing, a chamber ineach end of said housing, a piston intimately reciprocating inY said housing, a tool bit holder integralwith said piston, said holder and said piston being longitudinally disposed with respect to the longitudinal axis of said housing, said piston being of relatively small mass and small inertia with respect to said housing, said housing having an aperture in one end whereby the reciprocal motion of said piston in said housing may be transmit-ted to said tool bit hol-der to lprovide an operating force outside of said housing, a fluid inlet at the other end of said housing, .channel means in said housing andin vsaid piston for alternatively directing fluid from said inlet to each othenof said chambers to drive said piston in a forward stroke and in a return stroke, said channely meansv comprising a drive passage comrnunicatingwith said fluid inlet and having a pair of branches `terminating adjacent Said piston, a forward stroke passage communicating with one of said charnbers and terminating adjacent said piston, a return stroke passage communicatingwith the other of said chambers and terminating adjacent said piston, and groove means in said piston whereby movement of said piston causes said groove means to open and close communication of said drive passage with said forward stroke passage and said return stroke passage to permit said duid to alternately iiow to each of Vsaid chambers.

2. A pneumatic tool as set forth in claim 1 wherein said forward stroke passage islonger than said return stroke passage whereby said forward stroke is stronger than said Vreturn stroke.

3. A pneumatic tool comprising a slender elongated housing, a chamber in each end of said housing, a piston intimately reciprocating in said housing, a tool bit holder preciably longer than said piston,

ytively small mass and small inertia with integral with said piston, said holder and said piston being longitudinally disposed with respect to the longitudinal axis of said housing, said piston being of relarespectv to said housing, said housing having an aperture in one end whereby the reciprocal motion of said piston in said housing may be transmitted to said tool bit holder to provide an operating force outside of said housing, a duid inlet at thev other end of said housing, channel means in said housing and in said piston for alternatively directing fluid from said inlet to each of Said chambers to drive said piston in a forward stroke and in a return stroke, an exhaust port being in each of said` chambers, and the distance between said exhaust'ports being slightly longer than the length of said piston whereby one of said ports opens when the other of said ports closes.

4. A pneumatic ytool as set forth in claim 2 wherein resilient means are in each of said chambers for preventing said piston from striking said housing,V saidhousing including an inner shell and an outer shell, said inner shell containing a plurality of open passages, said outer shell covering said open passages, said passages comprising a portion of said channel means, an exhaust port being in each of said'chambers, the distance between said exhaust ports being slightly longer than the length of said piston whereby one of said ports opens when the other of saidports closes, said tool bit holder being apand substantially the entire length of said tool bit holder being mounted within said housing.

References Cited by the Examiner UNITED YSTATES PATENTS 537,646 4/95 YRinsche 91-232 538,433 4/95 Schmidt 91-232 5 49,5 14 l l/ 95 Keller 91-232 605,486 6/ 98 Katten 91-232 1,017,388 y2/12 Dickson 91-352 1,160,578 11/15 Clement 91--232 2,751,922 6/56 Miller 92-85 2,884,901 5/59 Chandler 91-232 2,944,521 7/'60 Kibbe 91-234 FOREIGN PATENTS 306,192 2/ 33 Italy.

3,969 8/ 91 Switzerland.

FRED ENGELTHALER, Primary Examiner. 

1. A PNEUMATIC TOOL COMPRISING A SLENDER ELONGATED HOUSING, A CHAMBER IN EACH END OF SAID HOUSING, A PISTON INTIMATELY RECIPROCATING IN SAID HOUSING, A TOOL BIT HOLDER INTEGRAL WITH SAID PISTON, SAID HOLDER AND SAID PISTON BEING LONGITUDINALLY DISPOSED WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID HOUSING, SAID PISTON BEING OF RELATIVELY SMALL MASS AND SMALL INERTIA WITH RESPECT TO SAID HOUSING, SAID HOUSING HAVING AN APERTURE IN ONE END WHEREBY THE RECIPROCAL MOTION OF SAID PISTON IN SAID HOUSING MAY BE TRANSMITTED TO SAID TOOL BIT HOLDER TO PROVIDE AN OPERATING FORCE OUTSIDE OF SAID HOUSING, A FLUID OUTLET AT THE OTHER END OF SAID HOUSING, CHANNEL MEANS IN SAID HOUSING AND IN SAID PISTON FOR ALTERNATELY DIRECTING FLUID FROM SAID INLET TO EACH OTHER OF SAID CHAMBERS TO DRIVE SAID PISTON IN A FORWARD STROKE AND IN A RETURN STROKE, SAID CHANNEL MEANS COMPRISING A DRIVE PASSAGE COMMUNICATING WITH SAID FLUID INLET AND HAVING A PAIR OF BRANCHES TERMINATING ADJACENT SAID PISTON, A FORWARD STROKE PASSAGE COMMUNICATING WITH ONE OF SAID CHAMBERS AND TERMINATING ADJACENT SAID PISTON, A RETURN STROKE PASSAGE COMMUNICATING WITH THE OTHER OF SAID CHAMBERS AND TERMINATING ADJACENT SAID PISTON, AND GROOVE MEANS IN SAID PISTON WHEREBY MOVEMENT OF SAID PISTON CAUSES SAID GROOVE MEANS TO OPEN AND CLOSE COMMUNICATION OF SAID DRIVE PASSAGE WITH SAID FORWARD STROKE PASSAGE AND SAID RETURN STROKE PASSAGE TO PERMIT SAID FLUID TO ALTERNATELY FLOW TO EACH OF SAID CHAMBERS. 